The present invention relates to a method and apparatus for providing storage of signal bursts on-board a satellite. More particularly, the invention relates to a switch matrix with a delay feature which may be used to temporarily store signal bursts on-board a satellite in a satellite-switched time division multiple access (SS-TDMA) environment.
In satellite communications, information is transmitted on an uplink channel from a fixed earth station or a mobile platform near the earth to the satellite from which it can be relayed on a downlink channel to another fixed earth station or mobile platform. In a number of important types of communication systems, it is desirable that the satellite not be required to immediately relay the uplink information on the downlink, but rather that it have the capability of storing the message for a short period until a more appropriate moment for transmission comes about.
In the part, methods for temporarily storing such signals on-board a satellite have been proposed which require elaborate signal processing to convert signals to a form appropriate for digital storage. In these systems, signals which arrive on the various uplinks are first demodulated so that the incoming signals are converted to baseband digital data. This information is then placed into digital memory where it is kept until needed. It is then read out or switched onto the appropriate downlink output, where it must be demodulated before it can be transmitted on the downlink.
This method of demodulation, storage and remodulation has several disadvantages. Increased complexity is introduced through the necessity of converting signals from their modulated form to digital data and then having to reconvert them back to modulated form. The processes of demodulation, remodulation and digital storage require the use of components which increase the mass and power requirements of the spacecraft payload. Further, extra precautions must be taken to ensure that the digital components employed are tolerant to or protected from the radiation environment of space.